1. Field of the Invention
The present invention relates to an endoscope which includes an endoscope insertion portion having an actively bendable bending portion.
2. Description of the Related Art
In recent years, in various fields such as the medical field and the industrial field, there has been utilized an endoscope having a long length endoscope insertion portion inserted into a subject. Such endoscope includes a type in which a bendable bending portion is provided on the distal end side of the endoscope insertion portion, and a bending mechanism for actively bending the bending portion is provided on the proximal end side of the endoscope insertion portion.
For example, in Japanese Patent Application Laid-Open Publication No. 2005-13613 (hereinafter referred to as Document 1), there is proposed an endoscope which includes, as the bending mechanism, a pulley rotated by a driving portion, an annular member rotatably arranged on the outer peripheral surface side of the pulley, and a pulling member whose intermediate portion is wound and arranged around the annular member in a state of being wound substantially one time, whose distal end portion is fixed to a bending portion, and whose proximal end portion is fixed to an operation portion.
In the endoscope having such bending mechanism, when the proximal end portion of the pulling member is pulled by the operation portion, the pulling member, which is wound around the annular member about one time, is hence pulled and moved so as to reduce the diameter of the annular member. Thereby, the annular member is brought into close contact with the pulley, so as to be rotated together with the pulley. As a result, the distal end of the pulling member is pulled and moved by the rotation of the pulley, so that the bending portion is bent in a predetermined direction.
However, in the bending mechanism of the endoscope as described in Document 1, when the pulling member is pulled and moved as described above, a portion of the pulling member which is extended from the operation portion and starts to be wound around the annular member, may be rubbed with a portion of the pulling member which is extended to the bending portion from the state of being wound around the annular member about one time.